This disclosure relates to processes for patterning and etching a substrate to form a complex three dimensional surface topography defined by a plurality of nanometer scale critical dimensions and devices manufactured using such processes.
Lithography (e.g., photolithography) is known and used for fabricating nanofluidic devices, integrated circuits, and the like. As an example, a typical nanofluidic device may include a fluidic channel with a nanometer scale depth for the manipulation and analysis of biomolecules, such as nucleic acids and proteins.
Currently, photolithography is one method that is used to fabricate such nanofluidic channels. For instance, a photoresist layer may be deposited onto a substrate and then exposed to a light pattern created using a photomask. The portions of the photoresist that are exposed to the light are either rendered resistant to a developer (i.e., when a negative photoresist is used) or soluble in the developer (i.e., when a positive photoresist is used). In either case, the developer removes the portions of the photoresist that are soluble to thereby expose the underlying substrate. The exposed portions of the substrate are then etched to a nanometer scale depth which may be enclosed to form a fluidic channel. Thus, one iteration of applying the photoresist, exposing the photoresist to the light pattern, and etching the substrate forms a mono-depth channel in the substrate. Traditional lithography is therefore planar with respect to the features formed in a single iteration. Additional channels or channel depths can be formed using additional iterations but require precise alignment of the photomask relative to the channels formed in prior iterations. Moreover, features from different iterations must overlap to form a continuous channel, which can result in multiple etches in the overlapping region that limit device design and functionality.
The inherent dimensional limitations on serial patterning and alignment limit the geometry, number and size of the channel depths that can be formed and prevent the fabrication of some complex three dimensional surface features. Indeed, since the utility of a nanodevice is in general proportional to its complexity and dimensionality, current devices provide relatively limited ability to manipulate biomolecules or other analytes of interest.